Composition and process for metal pickling



United States Patent AND PROCESS FOR METAL COMPOSITION PICKLING Ralph E. Plump, Pittsfield, Mass., and James w. Carroll,

Lafayette Hill, Pa., assignors to Pennsalt Chemicals Corporation, a corporation of Pennsylvania No Drawing. Original application February 11,-1950, Serial No. 143,822, now Patent No. 2,664,408, dated December 29, 1953. Divided and this application March 23, 1953, Serial No. 349,952

1 Claims. (01. 252- 149 This invention relates to metal pickling and to 'new' compositions particularly useful in this field.

The present application is a division of applicants copending application Serial No; 143,822, filed February 11,- 1950, which has now matured into "Patent No. 2,664,408, issued on December 29, 1953. r 1

In the pickling of metals, i. e. removal of scale or other metal oxidation'products from metal surfaces, it is customary to treat the metal with a dilute aqueous solution of a relatively strong acid such as sulfuric or hydrochloric acid. In prior art practices, a compound or compounds which exhibit inhibiting properties are usually incorpo rated in such. pickling acid in an eifort to lessen the attack v For example, various coal tar products, so

on the metal. sulfonated petroleum or alcoholic still residues, aromatic thiourea derivatives, and reaction products of certain aryl thioureas and an aldehyde have been stated to have in hibiting properties. It has also been suggested heretofore that the addition of such materials as cellulose pulp waste liquor and gelatin may increase the efliciencies of some pickling baths.

We have now discovered that the solid condensation products obtained by reacting urea, thiourea, or a mixture of urea and thiourea with a mixture of acidified sulfite pulp waste liquor and a water-soluble aldehydein the 2,823,184 Pat tented Feb. 11, 1958 tion product. Excellent results are achieved on metals such as various types of steels, iron, stainless steel, tinned steel, tinned copper, and tin.

In general, we incorporate our new condensation prod-- net in a pickling bath of the type customarily employed.

for'cleaning metal-objects, usually an aqueous solution containing from 1 to 50% by weight of a relatively strong: non-oxidizing inorganic acidsuch as sulfuric, phosphoricg.

hydrochloric'or hydrofluoric acid, preferably in 520%; by weight of sulfuric acid or 530% hydrochloric acid T In some instances beneficial results may be achieved by .1n-'- corporating our condensation product in aqueous mix-I tures of theseand other acids. Furthermore, ,we have presence of an acid catalyst exhibit markedly improved inhibiting properties against metal attack by acid pickling 5' baths containing non-oxidizing acids as compared to prior art products.

Though we do not wish to belimited by any theoretical explanation, it is believed that the surprisingly superior inhibiting properties of the products obtained may be at-;

trib'utcd in part to areaction in addition to the expected condensation of urea or thiourea with aldehyde, namely a chemical reaction between at least someof the constituents of the sulfite pulp waste liquorand one or more of the other constituents. The composition of sulfite. pulp waste liquor varies-somewhat with the source and e treatment, but usually consists of some inorganic materials such as calcium sulfate, calcium oxide and water, thioj acids, other acids, chiefly lignosulfopic acid and their calcium salts, lignin, dextrose, mannose, gums, albumins,

moreimportant constituents are believed to be lignosu ionic acid, lignin, dextrose, mannoseiand vanillinI .1 was" ever the explanation, we have found that the product of the above described reaction is markedly superior in metal pickling inhibiting properties to a-mixture'of the; 1 components, considered individually or in any combination thereof, e. g. a mixture of urea or thiourea-aldehyde condensation product and sulfite pulp waste liquor. Thus, in a typical instance, we found that a urea-formaldehyde sulfite waste liquor product made according to our inr; vention gave almost 50% increased metal protection as compared to equivalent quantities of a mixture of sulfitepulp waste liquor and a urea-formaldehydeeondensav found thatou'r new product may advantageously be ad- 7 mixed-with other materials known to aid or exhibit .ilI'. f'

hibiting properties? for "example, glue, sodium chloride and diphenylthiourea may be admixed therewith.

As illustrative 'ofa-method of. preparing our condensa 3 tion product, we mix urea, thiourea, or both, with sulfite pulp waste liquor and a water-soluble aldehyde in an acid reaction medium. Thus, urea and/or thioureamay 'be' dissolved in water and the other two reactants added theretotf' .The resulting mixture may then be acidified and the precipitate which forms separated and dried. paring the. condensation products of our present inventionthe sulfite pulp waste liquor used should preferably not contain more than 30 grams lignone (i. e. 15 gramsof the In prepulp waste liquor can be employed, excellent acidj-in'hibit 9. ing materials being obtained when concentrations 'as lovq T as 0.5 grams lignone-to 15grams of urea and/or thiourea are used.

The etfect of varying the amount of lignone in the cona i densation reaction is best illustrated by the tablegiven in Example 1. The products obtained in each instance were washed with-water, then with alcohol and air dried.

Each product wastest ed by using 0.025% by weight of the product in a picklingbath' of 10% sulfuric acid in which was immersed a steel strip, the bath being'maintained at a temperature of C. during the test.

-{ExA MPLE1- Variation of sztlfite pulp waste .liquor (lignone) concentration HCl catalyst The product preparedxaccording to. ouriinvention, is

incorporated "in a typical acid: pickling bath, either alone or in conjunction withotherF materials: which are known, to exhibit inhibiting properties. A'coinparativelylow con-- centration of our inhibitor is sufiicient to obtain good metal protection. The concentration required to achieve-a cer-..

tain' amountof metal protection will vary with the pi ekling,

Urea, Thiourea, Formalln, Llgnone, Weight Percent Grams Grams; Grams Grams 'Yield,-; Protection M' Percent 13.5 20.25 2.5 74.4' r 87.6'

13. 5 20. 25. 5.0 74.8 86.7 t 13.5 20. 25' 10.0- 74.2, 1386.9 13.5 20.25 15.0 74.0 87:0 13.5 -20. 25 a 20.0 69.2 86.6 13.5 20. 25 30,0. 69.1 s1.4

conditiongbut-th'e;quantity required issignificantly lower than that of h eretofore known inhibiting materials. Thus;

we have found that a concentration, in acid baths "ofjtd aaaaaeea.

v em as it eas 919.01% bm ht is efl etiveun.-.

der usual pickling conditions while about 0.025% by weight is the usual preferred concentration, and 0.10% is the lleuel max tnumamqua necess yeth ua m rezma be used, %b naabqut; heam ximumaamonntw ich will dissolve in the acid picklingbath To illustrate ou thQd'Qf Prepara i n by 1 p aifi example, we may dissolve 60 parts of urea andfi parts of thiourea in 89 parts of water. 89 parts of sulfite-pulp waste liquor (containing about 1 2%,soli ds);and;89 partsof 37% formaldehyde are added ,and thesolution stirred. Alternatively, a concentrated sulfite pulp-waste liquor may be used with acorresponding addition of waten; 1.5 parts'of hydrochloric acid are added with stirring. A precipitate soon forms which may be separated and washed with water, followed by oven drying at 100 C. The product so obtained is superior in inhibiting properties to those of the prior art, and may be admixedwith other materials of inhibiting value, such as diphenylthiourea, glue, etc. To 1.

obtain a preferred product we admix:

Our invention is notlimited to anyspecific reaction product resulting from the condensation reaction of a water-soluble aldehyde, sulfite pulp waste liquor,..urea, and/or thiourea since wehave found that the condensation reaction product will have superior acid inhibiting properties as long as a water-soluble aldehyde having less than two functional groups other than the aldehyde group is used, the aldehyde to urea and/ or thiourea ratio of the U reaction mixture is, maintained to within 0.1 to 5 mols al-, dehyde per mol of urea and/ or thiourea, and the concentration of the sulfite pulp waste liquor does not exceed 30 grams lignone, or 15 grams solid Waste liquor, per 15 grams of urea and/or thiourea employed. .The table of Example 2, which gives some of the reactionratios em-,v ployed, helpsfurther to illustrate the wide range of urea and/or thiourea reactants to aldehyde reactants that can be employed while practicing our invention. In studying this table, it shouldbe kept in mind that the lignone can be varied, as illustrated in Example 1, for each ratio of urea--and/ orthiourea to aldehyde given in Example 2,. However, for ease of illustration, the amount of urea and thiourea reactants of Example 1 has been kept constantv whereas the amount of lignone present in the reactants of Example 2 hasbeen kept constant. The resulting product of each of the reaction ratios given in Example 2 was found ontestingto ,be an excellent acid inhibitor.v The tests were carried out in the same manner as described for Example 1.

EXAMPLE 2 Urea'and thiourea-aldehyde reactions in the presence of sulfitepnlp waste liquor HCl catalyst Urea and Aldehyde, Mole Llgnone, Thlourea. Mols Grams 0.5 Formaldehyde 7. 5 0.1 Formaldehyde 7. b 1 Benzaldehyde 7. 5 5 Butyraldehyde. 7. 5 0.33 Butyraldehyde 7.5 1 Formaldehyde. 10.0 5 Formaldehyde. 10.0 0.125 Formaldehyde.-... 10. 0

In th fo lowin ples. w h. i l st a e. bu d n limit 101 ven h r pmpo t on o h sp e fic 93311 1.;

p s tf h e ga 5 d. nd i d na e th rei i gl as t i h b tor-f elossi w ght o thermal ernicklinani an wi outth p sence. o th inhibz.

itor gives the percent protection according to the expression:

(Weight loss uninhibited) (Weight loss inhibited) (Weight loss uninhibited) peratures strips of cold-rolled steel .in baths of 6%,hydro-;

chlorrqacrd contarnlng the tndrcated quantities of lnhlbrtor:

Percent Protection Inhibitor Concentration at (We ght perce t).v

the indicated quantities-of inhibitor:

Percent Protection-at the Indicated Inhibitor Concentration Sample r in Welghtlercent 7 EXAMPLE 5 These data..were,obtained by pickling, at 25 or 50 C.

strips; of stee.l .in 10% hydrofluoric acid baths containing various quantities of inhibitor:

I Percent-Protection Inhibitor- Concentration (Weight percent) 7 0 01 64. s 85. 0.05.. 76.5 87. n1n- 85.8 89.

I EXAMPLE 6 s e mpl nhows the ll tm a Prote p p:

asafs u r a tsw aans in relat v y h h strength r e d...p sling .b sti a d m stra s I je tebil t andlon la ti q alities-1 esed a. w r a ned b .Ri. ia --.etZ Z' -r s .str psl na b th o hydr fluq d. n a ni 9. 9%; y .w ehte o r ibitoaid th Malawi-time. d qata 1 Time .(hoursl Percent Protection 23 99. 72 99. 288 99. 40s g 99. 768 e 99.

im ar'p q lin qpa et on s w re ca rie ou e p oy inhibitor compositions made from urea in the absence of thiourea, fronrthiourea withouturea present, and from mixture s of urea and thiourea other than the .abovedescribed rnixtures, and marked improvement in metal proteetion was noted -in each case. Similarly, aldehydes othepthan formaldehyde, "e. g. acetaldehyde,:propionaldehyde; butyraldehyklqibenzaldehyde or -aldo1;- may be em ployed in thencondensation..reaction,-tand considerable modifieatieniis; possibleiin' the-choice of materials to be octane admixed with our condensation products without departing from our invention. I

Having thus described our invention, we claim:

1. In the process of pickling metal surfaces the improvement which comprises subjecting the surface to the action of an aqueous solution of a non-oxidizing pickling acid, said solution containing 0.001 to 7% by weight of a reaction product resulting from an acidified reaction mixture containing sulfite pulp waste liquor, water-soluble aldehyde and material selected from the group consisting of urea and thiourea, in which reaction mixture 0.1 to 5 mols of water-soluble aldehyde are present per mol of said material of said group and said sulfite pulp waste liquor contains not more than 1 gram of sulfite waste liquor solids per gram of material of said group.

2. The process of claim 1 wherein said surface is steel and said aldehyde is formaldehyde.

3. The process of claim 1 wherein said pickling acid has a concentration of 1 to 50%.

4. The process of claim 3 wherein said surface is steel and said pickling acid is sulfuric acid.

5. The process of claim 3 wherein said surface is steel and said pickling acid is hydrochloric acid.

6. The process of claim 3 wherein said surface is steel and said pickling acid is hydrofluoric acid.

7. The process of claim 3 wherein said surface is steel and said material of said group is urea.

8. The process of claim 3 wherein said surface is steel and said material of said group is thiourea.

9. A pickling bath comprising an aqueous solution of a non-oxidizing inorganic pickling acid, said solution containing 0.001 to 7% by weight of the condensation product resulting from an acidified reaction mixture of sulfite pulp waste liquor, water-soluble aldehyde, urea and thiourea in which reaction mixture 0.1 to 5 mols of aldehyde are present per mol of combined urea and thiourea and said sulfite pulp waste liquor contains not more than 1 gram of sulfite pulp waste liquor solids per gram of combined urea and thiourea.

10. A pickling bath comprising an aqueous solution of a non-oxidizing inorganic pickling acid, said solution containing 0.001 to 7% by weight of the condensation product resulting from an acidified reaction mixture of sulfite pulp waste liquor, water-soluble aldehyde, and urea in which reaction mixture 0.1 to 5 mols of aldehyde are present per mol of combined urea and said sulfite pulp waste liquor contains not more than 1 gram of sulfite pulp waste liquor solids per gram of urea.

11. A pickling bath comprising an aqueous solution of a non-oxidizing inorganic pickling acid, said solution containing 0.001 to 7% by weight of the condensation product resulting from an acidified reaction mixture of sulfite pulp waste liquor, water-soluble aldehyde, and thiourea in which reaction mixture 0.1 to 5 mols of aldehyde are present per mol of combined thiourea and said sulfite pulp waste liquor contains not more than 1 gram of sulfite pulp waste liquor solids per gram of thiourea.

12. A pickling bath comprising an aqueous solution of sulfuric acid containing 0.001 to 7% by weight of the condensation product obtained from an acidified reaction mixture containing sulfite pulp waste liquor, water-soluble aldehyde and materials selected from the group consisting of urea and thiourea, in which reaction mixture 0.1 to 5 mols of the water-soluble aldehyde are present per mol of said material of said group and said sulfite pulp waste liquor contains not more than 1 gram of sulfite waste liquor solids per gram of said material of said group.

13. A pickling bath comprising an aqueous solution of hydrochloric acid containing 0.001 to 7% by weight of the condensation product obtained from an acidified reaction mixture containing sulfite pulp waste liquor, water-soluble aldehyde and materials selected from the group consisting of urea and thiourea, in which reaction mixture 0.1 to 5 mols of the water-soluble aldehyde are present per mol of said material of said group and said sulfite pulp waste liquor contains not more than 1 gram of sulfite waste liquor solids per gram of said material of said group.

14. A pickling bath comprising an aqueous solution of hydrofluoric acid containing 0.001 to 7% by weight of the condensation product obtained from an acidified reaction mixture containing sulfite pulp waste liquor, water-s0luble aldehyde and materials selected from the group consisting of urea and thiourea, in which reaction -mixture 0.1 to 5 mols of the water-soluble aldehyde are present per mol of said material of said group and said sulfite pulp waste liquor contains not more than 1 gram of sulfite waste liquor solids per gram of said material of said group.

15. A pickling bath comprising an aqueous solution of phosphoric acid containing 0.001 to 7% by weight of the condensation product obtained from an acidified reaction mixture containing sulfite pulp waste liquor, watersoluble aldehyde and materials selected from the group consisting of urea and thiourea, in which reaction mixture 0.1 to 5 mols of the water-soluble aldehyde are present per mol of said material of said group and said sulfite pulp waste liquor contains not more than 1 gram of sulfite waste liquor solids per gram of said material of said group.

References Cited in the file of this patent UNITED STATES PATENTS 

9. A PICKLING BATH COMPRISING AN AQUEOUS SOLUTION OF A NON-OXIDIZING INORGANIC PICKLING ACID, SAID SOLUTION CONTAINING 0.001 TO 7% BY WEIGHT OF THE CONDENSATION PRODUCT RESULTING FROM AN ACIDIFIED REACTION MIXTURE OF SULFITE PULP WASTE LIQUOR, WATER-SOLUBLE ALDEHYDE, UREA AND THIOUREA IN WHICH REACTION MIXTURE 0.1 TO 5 MOLS OF ALDEHYDE ARE PRESENT PER MOL OF COMBINED UREA AND THIOUREA AND SAID SULFITE PULP WASTE LIQUOR CONTAINS NOT MORE THAN 1 GRAM OF SULFITE PULP WASTE LIQUOR SOLIDS PER GRAM OF COMBINED UREA AND THIOUREA. 